Pension Plans (Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Japan
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial gain (loss)	¥ 5,125	¥ 12,990	¥ 650
Amortization of net actuarial loss	(93)	59	79
Prior service credit due to amendments	(278)	0	881
Amortization of prior service credit	(72)	(84)	(47)
Settlements	(148)	0	0
Total recognized in other comprehensive income (loss), pre-tax	4,534	12,965	1,563
Overseas plans
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial gain (loss)	3,226	5,728	4,810
Amortization of net actuarial loss	9	11	9
Prior service credit due to amendments	(179)	(145)	(36)
Amortization of prior service credit	(322)	(354)	(329)
Amortization of transition obligation	1	1	1
Foreign currency exchange rate change	(78)	641	60
Total recognized in other comprehensive income (loss), pre-tax	¥ 2,657	¥ 5,882	¥ 4,515

Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income, Foreign Exchange Adjustment

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount, before tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, before tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.

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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for transition asset (obligation) of defined benefit plan.

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